A coder-decoder (CODEC) is essentially a data compression algorithm that selectively throws away information that it deems to be unimportant, while retaining the data that it deems necessary. The CODEC plays important role in the communications link. The CODEC must be robust enough to withstand a certain degree of data degradation during transmission. The better the CODEC is able to recover from bit errors, the more natural the reproduction will be over a wide range of conditions.
The original Code Division Multiple Access (CDMA) CODEC was not particularly robust, and as such it made even low Bit Error Rates audible to a discerning listener. CDMA providers began implementing a new CODEC called EVRC (which stands for Enhanced Variable Rate CODEC). EVRC permits more compressed signals (subscribers) to be stuffed into the same bandwidth. EVRC manages to produce reasonable audio quality in only 8 kilobits. Since individual EVRC users consume less bandwidth than users of the old CODEC, a CDMA “carrier” can accommodate more of them.